Hardening photographic emulsions



Patented July 11, 1939 UNITED STATES PATENT mm eater, N. Y.. m Jersey Ho Drawing.

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This invention relates to photographic'gelatin and to a method ior producing photographic gelatin and emulsions free from objectionable logging and "alter hardening."

It is customary to treat photographic gelatin or emulsion solutions or layers with a hardenin agent in order to increase the resistance of the gelatin or emulsion layer to swelling or softenin particularly when processed at increased temperatures. Compounds which have been used for this purpose are chrome alum, formaldehyde, and other reagents. In our prior Patent No. 2,059,817, granted November 3, 1936, we have also disclosed the use. of hydrosy aldehydes up to and including the pentoses for this purpose.

, .In many cases the degree of hardening produced by the addition of these hardening agents. as indicated by the melting point, swelling, behavlor-on photographic processing of the gelatin, and in other ways, is not complete after drying the product, but a greater or less amount of so-called "alter hardening occurs on storage of the plates or films. This after hardening" gives rise to a product whose properties are variable with time, unless an inconvenien'tlylong period a of storage prior to use is involved. This hardening may continue through a period of months and may equal or surpass in degree the initial hardening on ilrst drying. One consequence of this is a generally a reduction in speed of development,

properties may result, suchas fogging o! the plate or film.

It is therefore an object of the present invention to provide a photographic gelatin or emulsion which on storage will be stable against change in sensitometric properties 'or physical properties, suchas hardening and A further object is to provide a photographic emulsionwhich will not log on storage. A still lurther object is to provide a method of eliminating alter hardening" in photographic emulsions. A still iurther object is to provide a photographic emulsionwhich will be resistant to relativelyhigh processing temperatures without logging or de- 'lheseobiectsareaccomplishedaccordingtothe pruent' invention .by in thegela-.

ilnoremuiaionanaidehydehardeningagenttogetherwithoneormoreoiaclassofcompounds whichaloneposseslittleornohardeningeilect upon gelatin or geiatino-siiver halide emulsions, butinconiunctionwiththealdehydebothacceleratc thehardening action with elimination but other. objectionable changes in photographic talastmanlodakconi- .N.Y ..acorporationall lew Application September 2 5, 193,, Serial No. 1",! J

or reduction of aiterhardening" and also inhibit the tendency to-iog' production on storage or in- 1 cubation. These; added substances comprise homocyciic carbon containing one or] more phenolic The aldehyde hardeningLagentsmay include any of the well known such as formaldehyde, acetaldeh de'giycolaldehyde. aldol' or the straight-chain compounds disclosed in our prior Patent No. 2,059,817, granted November 3. 1936, such as arabinose.

The added homocyclic carbon compounds which we have found-suitable include phenolic compounds, such as mono-nuclear, mono-hydroxy, dihydroxyz and .trihydroxy derivatives; These may be substituted with one or more alkyl, alkoxy, sulionic acid, aldehyde, or carboxyl groups or hydrogen atoms. Nitro or .nitroso groups are undesirable because l bel-produce ex-' cessive absorption of actinic light.

' Among the di hydroxylated mono-nuclear bodies the 1:3 compound (resorcinol) .and its homologues are preferred to the 1:2 and 1:4 dihydroxy compoundsbecause of the greater stability, decreased tendency to log the emulsion. and reduced tendency to coloration by serial oxidation of 1:3 di-hydroxy compounds. Similarly, among the tri-hydroxy be'nsenes, .we prefer the symmetrical or 1:3:5 compound to 1:12;: tri-hydroxy benzene (Pyrogallol) or 1:2:4 tri-hydroxy benzene (oay-hydroquinone). 4

We also regardthe cognate naphthalene analogues as within the scope of our invention where they do-not introduce objectionable light absorption. The hydroxy naphthalene'compounds may a be substituted .in the same way as the mono-nuclear com v V customary todigest or pounds. Asiswellknownitis ripen a gelatino-silver halide photographic emulsion by the action of heator by, digestion with I ammonia before coating the emulsion on the sup port. According to'our invention the aldehyde hardening agent and the additional phenolic compoundare incorporated bymisingthem with the photographic emulsion at any stage after the digestion. either before or alter coating the .emuision onthesupport. The hardening agent and phenolic compound may beadded-to plain gelatin. such as that used for coating photographic supports, at any stage. I w The following table illustratesthe degree of hardening obtained by the meet various phenolic compoimdsin combination with various aldehyde hardening agents, together with the hardening obtained by the aldehyde alone. The hardening is measured by the melting point or the gelatin.

Concentration of Concentration ol aldehyde (on weight of ggg g g pH Mb hAldegelam) weight of gelatin) hyde g g only fi,

0.15% iormaldehydm 0.2% Phenol. 0. e2 74 0.1 lormaldehyde- 05% o-cresol 0.0 41 55 0.1 0 formaldehyde .25% more l 6. 0 41 05 .05% formaldehyde" liloro ueinol. 0.0 42-44 71 .1% formaldehyde- .l% p loro ncinoL. 4.0 42-44 85 .1% formaldehyde o thyinol 6.0 41 60 .1% iormaldehydo- .5% sodium phenol 0.0 41 68 sullonato. .15% formaldehyde.... .2? dsalicylic alde- 6.0 41 72 y e. .1% formaldehyde- 0.5% resorcinol 0. 7 68 .05% iormaldehyde-- A? dresorcyl alde- 4.0 60

Y 0. 4.0% aldol.-- 4.07 resorcinol 0.0 40 55 aldolo-lg 'ii resorcyl alde- 0.0 34 as y 0 1.0% aldol- 1.0 Jesorcyl aide 0.0 34 44 y e. 2.0% aldol 0. %dresoreyl alde- 0.0 36 62 y e. 3.0% phloroglucinol. 6.0 34 40 0.4% phloroglueinol. 6.0 34 40 1.0% aldol. 1.0% phloroglucinol. 8. 0 34 49 0.4% glycol aldehyde- 0.2h%esorcylic alde- 6. 0 39 63 y e. 0.4% glycol aldehyde... 0.5% phloroglucinol- 8. 0 05-70 80-84 1.0% arabinose-'. 1% resorcinol. 0. 7 34 38 The following specific examples illustrate the variation in hardening obtained, as indicated by the melting point of the gelatin, upon addition of an aldehyde hardening agent together with varying amounts of phenolic compounds.

55 on keeping with the mixture.

Example I Efiect of resorcinol on hardening of gelatin by formaldehyde.

Deashed gelatin-pH adjusted to 6.7.

Example I11 Effect of phloroglucinol on hardening of gelatin by formaldehyde.

Deashed gelatin at pH 6.7.

Formaldehyde 0.05 per cent of gelatin.

Amount of phloroglucinol (on weight of gelatin) gz flg gg This example again shows well marked optimum concentration eflect. This, however, is not objectionable to the practice of the invention, because there is stlll'sufllcient latitude for variations from the absolute optimum to be sufficiently efiective.

Example IV Eflect of resorcylic aldehyde on hardening oi gelatin by formaldehyde.

Gelatin adjusted to pH .9.

Formaldehyde 0.05 per cent of gelatin.

Formaldehyde 0.1 per cent of gelatin.

A olresorcylicaldehyde(onweightolgelatin) gg gg gg Amount o( rcsorcinol (on weight of gelatin) fl g g 0C 3.95. g 0129: "I: .I so a a 01. I 7 es 2.3%. 67

In addition to the phenolic compounds disclosed above we may use combinations of two The sample without "50min gradually harden phenolic compounds in certain cases. This has further, ultimately approaching much the same melting point as that attained by the mixtures. But this is only slowly attained (after-hardening) whereas the mixture gives nearly the maximum hardening at once. In addition, there is less 109 1 Example I! Elfect of'rmorcinol on hardening of gelatinosilver-halide emulsion by formaldehyde.

Emulsion'fadiusted to pH 6.6. Formaldehyde 0.1 per cent of gelatin in emulsion.

phenolic constituent as indicated in the above examples appears to be in harmony with this conception. While we believe this explanation of the reason for the action of the phenolic bodies in conjunction with hardening aldehydes to be as outlined. we do not reaard this theory as essential to the practice or our invention.

'lhe examples included in the above specification are not to be taken as limiting, since we regard our invention as coextensive with the scope or the appended claims.

What we claim is:

l. The method of producing a hardened ph graphic gelatin having slight after-hardening tendency which comprises imiiormly mixin comprises therewith prior to photographic processing an aliphatic aldehyde hardening agent and a homocylic carbon compound containing at least one nuclear hydroxy substituent group. i

2. The method of producing a hardened photographic gelatin having slight after-hardening tendency which comprises uniformly mixing therewith prior to photographic processing an aliphatic aldehyde hardening agent and a hydroxy benzene.

3. The method of producing a hardened photographic gelatin having slightafter-hardening tendency which comprises uniformly mixing therewith prior to photographic processing an aliphatic hardening agent and a phenol, 4. The method of producing a hardened gelatin having slight after-hardening tendency which uniformly mixing therewith an aliphaticaldehyde hardening agent and a 1-23-dihydroxy benzene.

5. The method of producing a hardened gelatin having slight after-hardening tendency which comprises uniformly mixing therewith an aliphatic aldehyde hardening agent and resorcylic aldehyde.

6. The method of producinga hardened gelatin having slight after-hardening tendency which 7. having slight after-hardening tendency -which comprises uniformly mixing therewith an aliphatic aldehyde hardening agent'and phloroglucinol.

8. In the manufacture ofa stable gelatin photo graphic emulsion, the step of hardening said gelatin with an aliphatic aldehyde hardening agent and a homocylic carbon compound containing at least one nuclear hydroxy substituent group, the aldehyde hardening agent and the homocylic carbon compound being uniformly mixed with the emulsion priorto development,

9. In the manufacture of a stable gelatin photographic emulsion, the step of hardening said gelatin with formaldehyde and a meta-cresol, the formaldehyde and the m-cresol being uniformly mixed with the emulsion prior to development.

10. In the manufacture of a stable gelatin photographic emulsion, the step of hardening said parent support and a gelatin emulsion'thereonr said emulsion containing as hardening means an aliphatic aldehyde hardening agentv and a homocylic carbon compound containing at least one nuclear hydroxy substituent group.

13. A photographic element comprising a transparent support and a gelatin emulsion thereon,

SAMUEL E. ana ram). mana'r c. noucx. 

